The present invention relates to a voltage level detector, in which a manner of light emitting means, e.g. light emitting diodes, known as "LEDs," or low voltage lamps, are located beside each other and are arranged to be selectively lit by means of a control circuit which functions to turn on each of the light emitting means at a different d.c. voltage level. Thus the voltage level is displayed visually and indicated in a stage like manner by the total number of light emitting means which become illuminated.
Especially in HiFi mixer systems for audio signals, for example, in an apparatus for making the sound track for moving pictures, or for helping a "Disc-Jockey" to give a professional presentation of his program material, there is a certain need for a momentary indication of the peak value of the signal in order to indicate for the operator the momentary state of the signal in each sound channel connected to the mixer. For a presentation of four channel functions, this can be accomplished by four rows of light emitting means such as the above-mentioned light emitting diodes (LEDs) arranged in the form of an X, in which the number of consecutively lighted LEDs in each row, starting from the cross point of the X, indicates the signal level. The greater the number of lighted LEDs, the higher is the signal level. For a number of channels greater than four, it is more practical to have the rows of LEDs for the separate channels arranged as parallel columns.
In earlier systems of this general type, the individual light emitting means of each row were connected electrically in parallel to a source of supply with the result that the current demand from the supply source varied in accordance with the number of light emitting means illuminated in each row. That is, the larger the number of illuminated light emitting means, the greater the current demand. Also the parallel connected light emitting means system was disadvantageous in that the illuminated signal level display unit suffered from a higher current consumption at the same time that the signal generation circuits also have a high current consumption.
It is very desirable to have as little current consumption as possible, especially when higher voltage levels are desired to be indicated, and it is also of a certain advantage to have a uniform current consumption since the need for the stabilizers can then be avoided, or at least the detector circuit does not by its current consumption adversely influence other circuits in an arrangement in which the detector circuit functions as a part.